Based on the investigation of damage results,including total collapse,partially collapse and other damage degrees in the same magistoseismic site near epicentro,the seismic design objective of \'collapse prevention in mega earthquake\' is proposed.

Using LS-DYNA960 non-linear finite element program,the author simulated numerically the effects of spalling and stopping tunnel induced by explosion on the top of rock tunnel.

The process of spalling under the attack by conventional explosions was simulated for the tunnel with the same rock condition and span in condition of supporting with and without SFRC respectively.

The goal of investigation of spalling failure is to establish the function relationship between the stresses on the surface of the spalling failure and the parameters of loading.

According to test results, all these damage shapes can generally be classified as impact crater, impact spallation, penetration perforation, impact perforation.

Under the condition of directly hit with precision-guided munitions,the research on the spall-resistant dam- age for underground structures has become important in protective engineering.

Research on the local response of spall for underground structures under blast loads was based on suppose of semi-infinite thickness of underground structures in the past.

This paper analyzes the astronomical background of the global huge earthquakes with M≥8.